Process for preparing hides



January 30, 1937.-

Patented Nov. 14, 1939 PATENT OFFICE PROCESS FOR PREPARING HIDES Otto Riihm, Darmstadt, Germany No Drawing. 'Application October 8, 1937, Serial No. 168,052. In'Germany December 29, 1936 "26 Claims. (01. 149-2) The invention relates to improvements in pre-' paring hides, and more particularly to a process for depilatin'g and bating skins and hides with the aid of mold tryptases.

The present application is a continuation-inpart of the following prior applications: Serial No. 70,890 filed March 25, 1936; SerialNo. 104,147 filed October 5, 1936i and Serial No. 123,295 filed In German application Serial No. R 97,257 filed September 4, 1936, and inniy U. S. application Serial No. 123,295 filed January 30, 1937, there is described a process for depilating and batl-ng skins and hides with the aid of mold tryptases especially tryptases cultured from aspergillus varieties, these being used in slightly I No. R 95,449 filed February 7, 1936, and in my U. S. application Serial No. 123,295, it is recited that the hides and skins may bepre-treated with sodium sulphite or similar sulphur-containing compounds, if desired, with the addition of soda, and then first subjected'to the action of the mold tryptasesolution together with chlorine-free and chromium-free oxidizing agents as activators. Pre-treatment with ammonia has been described in my German application Serial No. R 94,938 filed December 7, 1935 and in my U. S. application Serial No. 123,295.

The present application is related to the subject matter covered by' application Serial No. 123,295 in that the same reagents may be used but difiers from what is disclosed and claimed in said application in that the hair loosening or depilating agent is added in a separate step from the treatment with oxidizing and reducing agents. This step may be prior to the treatment with oxidizing agents, subsequent thereto or may be between the treatments with oxidizing and reducing agents.

Inaddition to the oxidizing and reducing agents recited, other agents could be used which facilitate the enzymatic action, e. g.,- wetting 'agents and organic compounds which contain hydroxyl groups, e. g., carbohydrates, alcohols, aliphatic oxy acids, phenols, naphthols.

Both in treating the skins with the mold tryptases as well as in the treatment with the recited inorganic substances, alkaline reacting I salts, e. g., sodium carbonate may be used conjointly therewith. However, a separate subsequent treatment with swelling or non-swelling alkalies and/or alkaline'reacting salts may be adjoined. I

An alkali nitrite, nitrate, perborate, percarbonate or peroxide, or hydrogen peroxide may for example serve as the chlorine-free and chromiumfree oxidizing agent used as set forth in my prior application Serial No. 123,295. In lieu of ammonia, ammonium salts such as ammonium chloride, ammonium sulphate, ammonium carbonate, may be used, together with alkaline reacting salts such as soda, sodium bicarbonate, borax, sodium phosphate, or alkalies like caustic soda or barium hydroxide.

Furthermore, the salt mixture may be used ccnjointly or separately for example so that the treatment with ammonia or with ammonia yielding salts either precedes or follows the treatment with the oxidizing and reducing agents.

This process is applicable both to salted as well as to dried skins. In working up salted skins it is preferable first to free these from adhering salt and to wash them out with water, whereupon they are soaked from leto 2 days with ordinary water, rinsed again, and then, in accordance with the invention brought directly into a solution of sodium nitrite, sodium sulphite, ammonium sulphate and soda.

In working up dried hides it has been found to be very desirable to allow a solution of oxidizing and reducing substances, if desired including ammonia, to act directly on the dried hides without a previous water soaking. Since the oxidizing and reducing acting compounds when used in this combination exert an appreciably greater softening action than water or neutral .salts or weak alkalies such as ammonia, the soaking period is appreciably shortened.

After such soaking it is possible to use other known depilating and bating agents in addition It has already been proposed to activate veg-l etable or animal proteases by means of thio' acids or their salts or even by means of other oxygen containing compounds which contain sulphur in dior tetravalent form and to use the enzyme solutions for depilating and bating of calf skins, using papain as the enzyme.

Furthermore it has been recommended to use papain in admixture with fungi tryptase for depllating and bating. Finally a method is known by which the depilating and bating are effected with the use of bacterial proteases, sodium bisulphite being indicated as the deliming or neutralizing agent.

It is also known that the action of papaln as a depilating agent can be increased by pre-treating the hides with strongly ionized salts such as e. g... sodium nitrate, potassium iodide, magnesium bromide, potassium cyanide, etc.

Aside from the fact, that owing to; the still relatively uncertain status of enzyme chemistry, it cannot be concluded from these proposals that pre-treatment with these compounds or their use conjointly with'enzymes will also produce favorable results with mold tryptases, nevertheless novelty is inherent in the process of the ap plication and consists in the combined use of oxidizing and reducing compounds, if desired to.- gether with ammonia, in a step separate from the treatment with the mold tryp'tases, thus producing unique and favorable results.

Example 1 Salted cattle hides are soaked for two days with ordinary water and then treated (per kg. of soft weight) with the following for one *hour:

.Water liters 200.0 Sodium sulphite kilogram .5 Ammonium sulphate "do---" .5 Sodium nitrite (in .6 Calcined soda do .45

The alkalinity of the solution corresponds to pH9 to 9.5. After reacting for one day, the hides are handled out and coated on both sides with a solution of Mold tryptase from Aspergillas I flaws kilog1'8m 1 Water-i liters 20 After 24 hours the hides are covered while in h the pit with a solution of:

Water liters-.. 200 Calcined soda kilograms 4 The alkalinity of this solution should be about pH 10. After 1 to 2 days the hides are depilated and then worked up without any subsequent batfor one hour, to which may then be added a solution of .5 kg. of sodium sulphite in 50 liters of water-the treatment continued again for an hour, and the procedure continued as indicated above.

Example 2 The procedyre is carried out as in the case of Example 1. In lieu of coating as described in subsequent hating.

that example, the hides are treated in a drum with:-

Water liters 200 Mold tryptase from Aspergillus wentii, -i kilograms 3 for one hour. The next day the following solution is addedthereto:

Calcined soda .-kilograms 4 Water.. liters are then worked up further as in Example 1.

Example 3 then stretched, and then placed in' a fresh soaking bath of the same composition. After 1 to 2 days, when sufliciently softened, they are limed with:

Mold tryptase from Aspergillus I eflusus kilnnrams 3 Water mars 10 The hides are placed in a pit and after 24. hours covered with:

Water liters 200 Calcined soda "kilograms" 4 After 5 days they -are depilated and worked up further without any subsequent hating.

Example 4 40 kg. of dry sheep skins are soaked in the manner indicated for Example 3, then coated o the fleshy side with:

Mold tryptase from Aspergillus oryzae kilograms 3 Water liters After 24 hours the wool is removed; then they are after-treated for two days (per 100 kg. of hide weight) with a solution of:

Water ers" 300 Calcined soda; kilograms.. 3

They are then worked up further without any Example 5 Salted cattle hides are soaked for two days with ordinary water, then treated for one hour (per100 kg. of soft weight) with:

Water liters 200.0 Sodium sulphite kilogram .5 Ammonium sulphate do .5 Sodium percarbonate do .6 Calcined soda do .4

The alkalinity of the solution should be pH 9.5. After reacting for one day the hides are handled out and coated as in Example 1 with the mold tryptase solution.

Ewample 6 The procedure is carried out as Example 5. In lieu of .6 kg. sodium percarbonate however, .6 kg. sodium perborateare used.

20 After 1 to 2 days the hides may be depilated and Example 7 Salted cattle hides are soaked for three days with ordinary water and then treated for one hour (per 100 kg.of soft weight) with:

Water liters 200 Mold tryptase from Aspergillus flaws kilograms 2 The next day a solution of Sodium sulphite "kilograms" 1 Sodium nitrite -J do 1 Ammonium sulphate do 1 Calcined soda do 6 Water liters 40 are added. After treating for one hour the hides are allowed to repose over night. The alkalinity of this solution should be pH 10. After one day the hides are depilated' and then worked up further without subsequent bating.

Example 8 The procedure is carried on as in Example 1. There is however added to the solution of sodium sulphite, ammonium sulphate, sodium nitrite and soda (per 100 kg. of soft weight) .3 kg. of olein alcohol sulphonate.

Example 9 The procedure is carried out as in Example 1. However, to the solution of sodium sulphite, ammonium sulphate, sodium nitrite and soda, .5 kg. of sodium lactate are added.

Example 10 40 kg. of dry goat skins are soaked for one day with:

Water liters 400 Sodium su1phite kilogram .4 Ammonium sulphate do .4 Sodium nitrite do .4 Soda (calcined) do .4

then stretched and placed in afresh soaking bath of the same composition, After 1 to 2 days the skins, if sufliciently softened, are limed as usual with lime-sodium-sulphide and bated with a pancreatic bating liquor.

I claim:

1. In a process which includes treating hides or skins in aqueous solution with (1) at least one oxidizing agent selected from a group consisting of alkali nitrates, alkali nitrites, alkali percarbonates, alkali peroxides and hydrogen 'peroxide, (2) a reducing agent comprising an oxygen containing sulphur compound and (3) a depilating and bating agent comprising a mold tryptase; the improvement wherein the treatment with the depilating and hating agent comprises a separate step from the treatment with the- 5. Process according to claim 1, wherein the said oxidizing agent'and the said reducing agent act on the hides or skins together in one solution. 6. Process according to claim 1, wherein the said oxidizing agent and the said reducing agent act on the hides or skins in separate solutions.

'7. Process according to claim 1, wherein the said oxidizing agent and the said reducing agent act on the hides or skins before the action of the depilating and bating agent.

8- Process according to claim 1, wherein the said oxidizing agent and the saidreducing agent act on the hides or skins after the action of the depilating and hating agent.

9. Process according to claim 1, wherein at least one member of a group consisting of alkalies, lime, and sulphides of the alkalimetals is used as the depilating agent.

10. Process according to claim 1, wherein mold tryptase in neutral to weakly alkaline aqueous solution is used as the depilating and hating agent.

11. Process for producing ready-to-tan hides or skins including the steps of soaking dry hides or skins in aqueous solutions of 1) oxidizingagents selected from a group consisting of alkali nitrates, alkali nitrites, alkali percarbonates, alkali peroxides and hydrogen peroxide and (2) oxygencontaining reducing compounds of sulphur and separately treating the soaked hides or skins with mold tryptase in neutral to weakly alkaline aqueous solution.

12. Process for producing ready-to-tan hides a or skinsincluding the steps of soaking dry hides or skins in aqueous solutions of (1) oxidizng agents selected from a group consisting of alkali nitrates, alkali nitrites, alkali percarbonates, alkali peroxides and'hydrogen peroxide and (2) oxygen-containing reducing compounds of sul- Y phur and ammonia or compounds which produce ammonia and subsequently treating the soaked hides or skins with mold tryptase in neutral to weakly alkaline aqueous solution.

13. Process for producing ready-to-tan hides or skins including the steps of soaking salted hides or skins in water, treating the soaked hides or skins with (1) oxidizing agents selected from a group consisting of alkali nitrates, alkali nitrites, alkali percarbonates, alkali peroxides and hydrogen peroxide and (2) oxygen-containing reducing compounds of sulphur in aqueous solution and separately treating the hides and skins with mold tryptase in neutral to weakly alkaline aqueous solution.

14. Process for producing ready-to-tan hides or skins including the steps of soaking salted hides or skins in water, treating the soaked hides or skins with (1) oxidizing agents selected from a group consisting of alkali nitrates, alkali nitrites, alkali percarbonates, alkaliperoxides and hydro gen peroxide and (2) oxygen-containing reducing compounds of sulphur and ammonia or compounds which produce ammonia in aqueous solution and separately treating the hides and skins with mold tryptase in-neutral to weakly alkaline aqueous solution.

15. Process for producing ready-to-tan hides or skins including the steps of treating hides or skins with oxidizing agents selected from a group aqueous solution and depilating the hides or skins. 16; Process, for producing ready-to-tan hides or skins including the steps of treating-hides or skins with'oxidizingagentsselected from a group consisting of alkali nitrates, alkali nitrites, alkali percarbonates, alkali peroxides and 1 hydrogen peroxide together with oxygen-containing reduc'- ing compounds of sulphur, in an aqueous solution, separatelydepilating the hides or skins and treating them with alkaline compounds selected from agroup consisting of alkaiies and alkaline react- 17, Process -for producing ready-to-tan hides or skins including the steps of treating hides or skins with oxidizing agents selected from a group consisting of alkali nitrates, alkali nitrites, alkali.

percarbonates, alkali peroxides and hydrogen peroxide together with oxygen-containing reducing compounds of sulphur, in an aqueous solution, and thereafter with alkaline compounds selected from a-group consisting of alkalies and alkaline reacting salts, and depilating the hides or skins.

18. Process for producing ready-to-tan hides or skins including the steps of treating hides or skins with a water-soluble sulphite, and an alkaline nitrite in aqueous solution and separately treating them with mold tryptase from an aspergillus in neutral to weakly alkaline solution.

19. Prdcess for producing ready-to-tan hides or skins including the steps of treating hides or skins-with oxidizing agents selected from a group consisting of alkali nitrates, alkali nitrites, alkali percarbonates,alkaliperoxides and hydrogen peroxide together with oxygen-containing reducing compounds of sulphur and with a member of a group consisting 01 ammonia and compoundswhich produce ammonia, in an aciueous solution,-

separately treating the hides or skins with mold tryptase in neutral to weakly alkaline aqueous solution and depilatingthe hides or skins.

20. Process for producing ready-to-tan hides or skins including the steps-of treating hides o1 skins'with oxidizing agents selected from a group consisting of alkali nitrates, alkali nitrites, alkali percarbonates, alkali peroxides and hydrogen peroxide together with oxygen-containing reducing compounds of sulphur and with a member of a group consisting of ammonia and compounds which produce ammonia, in an aqueous solution, separately depilating the hides or skins and treating them with alkaline compounds selected from a group consisting of alkaiies and alkaline reacting'salts. i 21. Process for producing ready-to-tan hides or'skins including .the steps of treating hides or or skins including the steps of treating hides or skins with a water-soluble sulphite, an alkaline nitrite, an ammonium salt and an alkaline reacting salt in aqueous solution and separately treating them with mold tryptase from an aspergillus in neutral to weakly alkaline solution.

23. In a process which includes treating hides oxidizing agent selected from a group consisting of alkali nitrates, alkali nitrites, alkali percarbonates, alkali peroxides and hydrogen peroxide, (2) a reducing agent comprising an oxygen containing sulphur compound and (3) ,a depilating agent; the improvement wherein the treatment with the depilating agent comprises a separate step from the treatment with the oxidizing and reducing agents. p

24; A process according to claim 1 wherein a carbohydrate acts on the hides or skins separately from the depilating and bating agent.

2 5.A process according to claim 1, wherein an alcohol acts on the hides or skins separately from the depilating and hating agent.

26. A process according to claim 1, wherein an aliphatic hydroxy-acid acts on the hides and skins separately from the depilating and hating agent.

o'r'ro RGHM.

or skins in aqueous solution with (1) at least one 

